Communications terminal

ABSTRACT

A communications terminal, in particular a mobile radio station, having an AF amplifier stage, which includes a gain adjustment for adjusting the gain factor as a function of the speech volume.

BACKGROUND OF THE INVENTION

In the past, telephone connections were generally operated fromstationary terminals, which are normally installed in locations whichare relatively well shielded from environmental noise (within rooms,telephone booths). However, the explosive growth of mobile telephony hasnow resulted in a primary factor being the need to set up and maintaintelephone connections even in extremely poor acoustic conditions whichare varying rapidly and severely. The AF amplifier stages in modernterminals, in particular in mobile radio terminals, are thus equippedwith systems, which can be operated manually or under menu control, foradjusting the volume of the receiver capsule. The user can use theappropriate adjustment key or menu function to manually correct theinstantaneous receiver volume when the acoustic environmental conditionsare varying.

These manual corrections are, to a greater or lesser extent, cumbersome,and menu-controlled adjustment processes require the necessity tomonitor the display area on the terminal, thus resulting in thenecessity to at least briefly interrupt the communication.

In addition, the correction process must be repeated whenever there isany significant change in the environmental volume and, in the end, thismakes it considerably more difficult to hold a smooth conversation whileconcentrating on it. Finally, the necessity to manually correct thereceiver volume in certain situations, for example while driving avehicle or while operating a machine, involves a certain safety risk.

Thus, in practice, the adjustment capabilities available with the priorart frequently are not used.

The present invention is, therefore, directed toward specifying acommunications terminal in which the receiver volume is matched easilyand more safely to the environmental conditions.

SUMMARY OF THE INVENTION

The present invention includes knowledge relating to psychoacousticrelationships, which can be outlined as follows:

Let us assume there is a voice connection between a subscriber A who isusing a mobile telephone in a city area while the environmental volumeis fluctuating severely, and a subscriber B has a communication partner,who may himself use any desired terminal. At the subscriber A end, theenvironmental noise increases (for example, due to an increase in roadnoise, aircraft noise, a train going past etc.), while the voiceconnection is in existence. The subscriber A reacts to this byinvoluntarily increasing the volume of his speech. Conversely, thesubscriber A reacts to a reduction in the volume of the environmentalnoise by involuntarily speaking more quietly. This behavior issupposedly due to the fact that, when two conversation partners locatedat the same point are talking, the change in the environmental volumeaffects both of them to the same extent, and the comprehensibility ofone's own words for the person one is conversing with, on the one hand,and a volume level which is as reasonable as possible, on the otherhand, can be ensured by adaptation of the speech volume. However, in thecourse of a telephone connection, such behavior which is intended fordirect personal conversations makes only limited sense sincenoise-compensated transmitter capsules in telephones are matched to thenearby area, and changes in the environmental volume are passed on tothe subscriber B only in very attenuated form. The subscriber B,therefore, perceives the fact that the subscriber A is raising andlowering his voice as being at least unmotivated, if not annoying.

However, the outlined relationship opens up the technical capability toadjust the receiver volume of a telephone by detecting the speech volumeof the user on this telephone. Surprisingly, this means that there is noneed to separate the environmental noise from the user's speech, whichis technically difficult and at least complex. It has been found to besufficient to detect the speech volume and to actuate the gainadjustment in the AF amplifier stage via a control signal, which isderived from this detection, for adjustment of the gain factor.

In one simple and expedient embodiment, the transmitter capsule of thetelephone is directly followed by a level or voltage measurement device,which detects the speech volume.

Adapted processing of the primary measurement signal in order to avoidundesirable gain changes and control oscillations in thespeech/listening system resulting from natural volume fluctuations whilethe user is speaking and during pauses in speech require a certainamount of care. For this purpose, the volume signal must expedientlyfirst of all be averaged using a suitably selected time constant, forexample in the region of seconds. Pauses in speech must be consideredseparately, for example by deactivation of the signal evaluation when apredetermined threshold level is undershot. In general, the establishedmobile radio standards provide functions which can be used for thispurpose. For example, the functionality of a GSM voice coder and decoder(CODEC) include what is referred to as the DTX Mode (DiscontinuousTransmission), in which the transmitter is activated only when aspecific speech frame (20 ms for GMS) actually includes spokeninformation. In principal, this function also can be used to excludepauses in the user's speech from the evaluation of the speech volume.

In an embodiment which can be flexibly matched to the normal speechcharacteristics of the user or to the area in which the telephone isbeing operated at that time, the averaging interval and/or thedeactivation threshold value are/is adjustable manually or under menucontrol. Thus, for example, the deactivation threshold value can beincreased when using a mobile station with a sensitive transmittercapsule when the environmental volume level is high (in trafficconcentrations, in production areas where the noise levels are high, incoastal areas etc.), to take account of this, and the individualadjustment of the averaging interval allows the preselection of a fairlysensitive or inert response for the gain setting, as a function of theuser's personal lifestyle.

In a further advantageous embodiment, parts for detecting the speechvolume or for gain adjustment are designed such that they can beswitched off as a function thereof, so that the telephone also can beoperated with a fixed AF gain setting, or can be changed to manual gainadjustment.

In a further embodiment, the area in which the volume level of thereceiver capsule can vary as a function of the environmental noise canbe predetermined as a subregion (“window”) within the overall range ofthe feasible receiver capsule volume, or the overall AF level range. Inaddition, in this embodiment, the presence of parts for shifting thiswindow, as required, within the overall level range is advantageous. Theparts for carrying out this shift can once again be operated manually bya switch, or under menu control. As an alternative to this, automaticshifting is feasible, as a function of a defined parameter, for examplethe reception field strength in a mobile station.

Detection of the dynamic response in the user's speech can also, in onespecific embodiment, provide an additional control signal not only forpositioning the “level window” but also for specific adaptive averagingof the speech volume.

One advantageous development of the present invention also provides forthe effect of varying the speech volume when the environmental noiselevel changes, which is irritating to the conversation partner in atelephone connection (and which the other subscriber receives only to avery restricted extent especially when using a noise-compensatedmicrophone in the transmitter capsule of his conversation partner) to beat least partially compensated for. For this purpose, a control stage isexpediently provided which is connected to the input of the AF amplifierstage, where the undesirably fluctuating signal level is present.

In one preferred embodiment, this control stage also can be selectivelyactivated or deactivated via a switching element or under menu control,in order to allow matching to the user's listening characteristics.

Additional features and advantages of the present invention aredescribed in, and will be apparent from, the following DetailedDescription of the Invention and the Figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows in block diagram form various components of a mobiletelephone to which the present invention is directed.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows, in the highly simplified form of a functional blockdiagram, those components which are essential to the explanation of thepresent invention in a mobile telephone 1, including a receiver capsule3 with a load speaker 3 a, a transmitter capsule 5 with anoise-compensated microphone 5 a, and an AF amplifier stage 7 with an AFsignal input 7 a.

In addition to being connected to the AF amplifier stage 7, the AFsignal input 7 a is connected via a first electronically controllableswitch 9 to an AF level control stage 11, whose output is connected to afirst control input 7 b of the AF amplifier stage 7.

The transmitter capsule 5 is connected via a second electronicallycontrollable switch 13 to a voltage measuring device 15 for detectingthe actual level of the speech volume at the microphone 5 a. The outputof the voltage measuring device 15 is connected to an averaging stage17, which is connected via a control input to the output of an averaginginterval adjustment device 19. On the output side, the averaging stage17 is connected firstly to a gain adjustment stage 21, and secondly toone input of a speech level component unit 23, whose other input isconnected to a speech level threshold value memory 25, and whose outputis connected via a third electronically controllable switch 27, forcontrol signal purposes, to a fourth switch 29, which makes or breaksthe connection between the averaging stage 17 and the gain adjustmentstage 21 as a function of the output signal from the speech levelcomparator unit 23 and the position of the third switch 27.

The gain adjustment stage 21 is associated, via a control input, with again range preselection stage 31, and the gain selection stage isconnected on the output side to a second control input 7 c of the AFamplifier stage 7. The output of the AF amplifier stage 7 is connectedto the loudspeaker 3 a of the receiving capsule 3.

The first, second and fourth controllable switches 9, 13 and 29 as wellas the averaging interval adjustment device 19 and the gain rangepreselection stage 31 are actuated via a microcontroller 33 of themobile telephone, which is connected in the normal way to its inputkeypad or keyboard 35 and to the display 37, and which has an associatedprogram memory area (ROM) 33 a and a main memory area (RAM) 33 b.

This arrangement operates as follows: the AF level control stage 11,which fundamentally operates in the same way as automatic level control,as is known per se, produces (depending on the specific configuration)partial or complete compensation for fluctuations in the input level atthe AF signal input 7 a, provided the first switch 9 is closed, and thisfunction is hence activated. This compensates, in particular, forincreases or reductions in the speech volume of the conversation partnerin a telephone connection resulting from environmental noise.

If the second switch 13 is closed, and the function of automaticmatching of the receiver volume to the speech volume is thus activated,the voltage measuring device 15 detects the speech volume level, withthe output signal from the voltage measuring device being subjected inthe averaging stage 17 to averaging using an averaging time intervalwhich is preselected via the averaging interval adjustment device 19 andis preferably in the range between 1 and 10s. This prevents the AF gainfrom being influenced by brief pauses in speech between individual wordsor sentences or by natural level fluctuations in the course of theconversation, with the preselection of an averaging time interval viathe keyboard or keypad 35, the microcontroller 33 and the averaginginterval adjustment device 19 allowing specific matching to normalspeech characteristics of the user or the specific situation in whichthe mobile telephone is being operated.

The output signal from the averaging stage 17 is subjected, in thespeech level comparator unit 23, to level discrimination using athreshold value that is stored in the speech level threshold valuememory, provided this function is activated by closing the third switch27. If the volume level of the microphone 5 a falls below thepredetermined threshold value, then opening the fourth switch 29 resultsin the corresponding conversation phase being excluded from theautomatic gain adjustment process. As soon as the speech level is onceagain above the threshold value, the output signal from the comparatorunit 23 changes, following which the fourth switch 29 is closed again,and the subsequent phase of the conversation is included in the processby transmitting the output signals from the averaging stage 17 to thegain adjustment stage 21 for the AF gain adjustment.

In addition, as for the other functions and possibly including menucontrol with the aid of the display 37, the gain range preselectionstage 31 also results in preselection, via the keyboard or keypad 35 andthe microcontroller 33, of a gain range or “level window” within whoseboundaries the gain adjustment stage 21 is intended, in response to theoutput signal from the averaging stage 17, to adjust the gain of the AFamplifier stage 7 via its second control input 7 c.

The embodiment of the present invention is not restricted to thedescribed exemplary embodiment, but is also feasible in a large numberof modified versions. For example, in simplified embodiments, there isno need for some or else all of the described switching and adjustmentfunctions, or these functions can be provided by conventional electricalswitches or adjustment controllers. The present invention can beimplemented not only in a mobile telephone but also, in particular, in acordless telephone or in a normal land line terminal.

It is self-evident that the described functions can to some extent beimplemented in the form of software. In this context, the wide range ofspeech processing functions in the protocols of modern mobile radiosystems offer worthwhile capabilities which largely results in therebeing no need for any additional hardware complexity. If a digitalsignal processor (DSP) is available, the functions described above canbe carried out with high precision, and dependent only on the software.

The method of the present invention can be applied, in addition totelephones, in general to all communications appliances using simplex orduplex speech operation (that is to says also including, for example,door interphones or the like).

Although the present invention has been described with reference tospecific embodiments, those of skill in the art will recognize thatchanges may be made thereto without departing from the spirit and scopeof the invention as set forth in the hereafter appended claims.

1. A communications terminal, comprising: a transmitter capsule; a receiver capsule; an AF amplifier stage, operatively coupled to the transmitter and receiver capsules; a gain adjustment stage for varying a gain factor of the AF amplifier stage in order to adjust receiver volume; a speech volume detection device operatively coupled to the gain adjustment stage; and a voltage measurement device as part of the speech volume detection device, the voltage measurement device being associated with the transmitter capsule and having a downstream averaging stage for averaging the detected speech volume, wherein the gain factor of the AF amplifier stage is adjusted as a function of averaged speech volume.
 2. A communications terminal as claimed in claim 1, wherein the communications terminal is a mobile radio station.
 3. A communications terminal as claimed in claim 1, wherein the downstream averaging stage has an averaging interval between 1 and 10s.
 4. A communications terminal as claimed in claim 1, further comprising: an averaging interval adjustment device which is operable either manually or under menu control via an operation control unit.
 5. A communications terminal as claimed in claim 4, wherein the averaging interval adjustment device and the gain range preselection stage have a control signal input for automatic activation and adjustment as a function of a control signal produced outside the AF amplifier stage.
 6. A communications terminal as claimed in claim 1, further comprising: a switch which is operable either manually or under menu control via an operation control unit for activation and deactivation of either the speech volume detection device or the gain adjustment stage.
 7. A communications terminal as claimed in claim 1, further comprising: a processor associated with the speech volume detection device for taking account of pauses in speech.
 8. A communications terminal as claimed in claim 1, wherein the gain adjustment stage includes a gain range preselection stage for defining an adjustment window within an overall variation range of the gain factor.
 9. A communications terminal as claimed in claim 8, wherein the gain range preselection stage is operable either manually or under menu control via an operation control unit.
 10. A communications terminal as claimed in claim 1, further comprising: a gain control stage for at least partial compensation for level changes at a signal input of the AF amplifier stage.
 11. A communications terminal as claimed in claim 10, wherein the gain control stage is operable either manually via a switching element or under menu control via an operation control unit. 